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The clustering of Hα emitters at z=2.23 from HiZELS

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<mark>Journal publication date</mark>11/10/2012
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number1
Number of pages11
Pages (from-to)679-689
Publication StatusPublished
Early online date1/10/12
<mark>Original language</mark>English


We present a clustering analysis of 370 high-confidence Hα emitters (HAEs) at z = 2.23. The HAEs are detected in the Hi-Z Emission Line Survey (HiZELS), a large-area blank field 2.121μm narrow-band survey using the United Kingdom Infrared Telescope Wide Field Camera (WFCAM). Averaging the two-point correlation function of HAEs in two ∼1° scale fields [United Kingdom Infrared Deep Sky Survey/Ultra Deep Survey (UDS) and Cosmological Evolution Survey (COSMOS) fields] we find a clustering amplitude equivalent to a correlation length of r 0 = 3.7 ± 0.3h -1Mpc for galaxies with star formation rates of ≳7M yr -1. The data are also well-fitted by the expected correlation function of cold dark matter (CDM), scaled by a bias factor: ω HAE = b 2ω DM where b=2.4-0.2+0.1. The corresponding 'characteristic' mass for the haloes hosting HAEs is log(M h/[h -1M ]) = 11.7 ± 0.1. Comparing to the latest semi-analytic galform predictions for the evolution of HAEs in a ΛCDM cosmology, we find broad agreement with the observations, with galform predicting an HAE correlation length of ∼4h -1Mpc. Motivated by this agreement, we exploit the simulations to construct a parametric model of the halo occupation distribution (HOD) of HAEs, and use this to fit the observed clustering. Our best-fitting HOD can adequately reproduce the observed angular clustering of HAEs, yielding an effective halo mass and bias in agreement with that derived from the scaled ω DM fit, but with the relatively small sample size the current data provide a poor constraint on the HOD. However, we argue that this approach provides interesting hints into the nature of the relationship between star-forming galaxies and the matter field, including insights into the efficiency of star formation in massive haloes. Our results support the broad picture that 'typical' (≲L {black star}) star-forming galaxies have been hosted by dark matter haloes with M h ≲ 10 12h -1M since z ≈ 2, but with a broad occupation distribution and clustering that is likely to be a strong function of luminosity.